A generalized appartus was designed and developed to measure high temperature-high pressure vapor-liquid-equilibrium (VLE), gas solubility, and pressure-volume-temperature (PVT) data for compounds and mixtures which are of interest in coal liquefaction processes. The heart of the apparatus was a novel variable volume equilibrium cell which consisted of a precision positive displacement pump in which the pump's cylinder itself was utilized as the equilibrium cell. V-L-E data on H(,2)-Tetralin systems were measured at 150(DEGREES), 189.6(DEGREES), and 268.7(DEGREES)C. The pressure range was 19.5 to 321.43 atm. The solubility of H(,2) in 2-ethylanthraquinone was measured at 150(DEGREES), 200(DEGREES), and 250(DEGREES)C and for pressures up to 247.69 atm. Molar volumes of saturated liquid tetralin were measured from 93.79(DEGREES) to 224.64(DEGREES)C. Compressibility factors were measured for benzene at 158.56(DEGREES), 181.68(DEGREES), and 202.64(DEGREES)C. The saturated molar volumes at each temperature were obtained from the intersection of each isotherm with the respective vapor pressure. These values were used along with a literature vapor pressure correlation('64) to calculate the enthalpy of vaporization, (DELTA)H(,(V)), of benzene at the three temperatures. The values of (DELTA)H(,(V)) were 137.4, 127.3, and 120.8 Btu/1bm at 158.56(DEGREES), 181.68(DEGREES), and 202.64(DEGREES)C, respectively. The corresponding values calculated by Organic('54) were 139, 130, and 120 Btu/1bm. Vapor pressures of the following six compounds were measured on another apparatus designed by Dr. S. C. Hwang of this laboratory: Tetralin, from 82.29(DEGREES) to 267.20(DEGREES)C; m-cresol, from 114.98(DEGREES) to 322.48(DEGREES)C; Naphthalene, from 91.44(DEGREES) to 295.01(DEGREES)C; 2-methylnaphthalene, from 130.22(DEGREES) to 325.34(DEGREES)C; Biphenyl, from 71.43(DEGREES) to 327.54(DEGREES)C; and Quinoline, from 64.96(DEGREES) to 328.14(DEGREES)C. A zone purification apparatus was designed and fabricated to purify the compounds used in VLE, PVT, solubility and vapor pressure measurements. The Grayson-Streed('31) (GS) and the Modified Regular Solution Theory (MRST)('30) were used to predict the VLE data for H(,2)-Tetralin systems. The predictions from the two correlations were compared with the data obtained in this work. The predictions from Riedel, Frost-Kalkwarf-Thodos and Nieto-Thodos vapor pressure correlations were compared with the experimental data obtained in this work. In general, if the temperature is not close to the triple or the critical points, all these correlations predict vapor pressures within (+OR-)5% of the experimental data.